Preheat the oven to 355F/180C.
Mix together all the ingredients except the water, then add the water and mix to combine well.
Then pour the batter onto a 'buttered' or parchment-lined 8" (inch) cake pan.
Bake in the oven for 30 minutes. It's really important that you do not open the oven during those 30 minutes, otherwise the cake will sink.
After 30 minutes, check the cake by inserting a toothpick, or cake tester. If it comes out clean, the cake is ready. If not, cook for 5-10 more minutes.
Leave to cool in the pan, then put the pan with the cake in the fridge for a minimum of 2 hours. ( This part is really important, because if you start icing the cake now, it will crumble, and it will be really difficult to ice it. )
Meanwhile - make the icing.
Mix together all the icing ingredients under the ingredient section above 'Icing' It should form a smooth icing.
When the cake is cold, remove gently the cake from the pan and then you have two options:
Slice the cake in half using a serrated knife, then ice the middle and the top, even the sides if you like.
Don't slice the cake, just ice the top and the sides is your other option.
Cover the cake with the icing you made, and decorate the cake however you like. I went for chocolate shavings and homemade vegan chocolate truffles.